Method for measuring odor level in natural gas

ABSTRACT

A method and apparatus which is particularly applicable to directly and objectively measure odor level in natural gas. The apparatus responds selectively to sulfur compounds in natural gas and produces an output signal proportional to the odor level of the gas, in the same manner as an &#39;&#39;&#39;&#39;average&#39;&#39;&#39;&#39; nose. A set of odor intensity factors developed empirically are applied to the output signal to provide a numerical value which expresses odor intensity of the gas in terms of a reference odorant compound.

United States Patent Kniebes et al.

1151 3 3,686,930 1 Aug. 29, 1972 [54] METHOD FOR MEASURING ODOR LEVEL INNATURAL GAS [72] Inventors: Duane V. Kniebes, La Grange; John AdrianChisholm, Maywood; Robert C. StlIbbS, Oak Forest, all of Ill.

73 Assignee: Institute of Gas Technology,

Chicago, Ill.

[22] Filed: May 7, 1970 [211- Appl. N0.: 35,489

52 US. c1. ..73/23.1,73/23, 23/232 0 51 Int. cl. .3. ..G0ln 31/08, 0011133 22 [58] Field of Search ....73/23.1, 23-, 23/232 R, 232 c,

[56] References Cited UNITED STATES PATENTS,

3,095,728 7/1963 Kindred et al. ..73/23.1 3,489,498 1/1970 Brody..356/187 OTHER PUBLICATIONS Instrument Data Folder No. 143,Instrumentation Laboratory, lnc., Watertown, Mass. 1

Determination of Petroleum Wax Odor by Chromatography, L. R. Durrett,Analytical Chemistry, Vol. 38, No. 6, May, 1966, pp. 745- 748. 1

Primary Examiner-Richard C. Queisser Assistant Examiner-C. E. Snee, IIIAttorneyDominik, Knechtel & Godula [57] ABSTRACT A method and apparatuswhich is particularly applicable to directly and objectively measureodor level in natural gas. The apparatus responds selectively to sulfurcompounds in natural gas and produces an output,

signal proportional to the odor level of the gas, in the same manner asan ave'rage? nose. A set of odor intensity factors developed empiricallyare applied to r the output signal to provide a numerical value whichexpresses odor intensity of the gas in terms of a reference odorantcompound.

PATENTEDmszs m2 3.686330 sum 1 or 3 EXHAUST FIG. 2

9;, FIG. 3 34 o I I I l {I I I. Jim k LM} I) X 45 46 47 INVENTORS DuaneV. Kniebes J. Adrian Chisholm BY Robert C. Stubbs ATTYS.

PAIEmmmczs I972 sum 2 or 3 7 P 4 E w M m G 0 I M M I||l..| F 1p m a. WAm fi m 3 I||||| 1.lIl-IIR 0 0 a E 2 S E L 4 H w D 0 7 /L|| m Y C, m o N7 E A m M O- x s 5 A 6 w 3 ill-I'll LIQUID SAMPLE INJECTION PORT TIME,minutes IN VENTORS Duane V Kniebes J. Adrian Chisholm Robert C. SfubbsATTYS.

PAIENTEDmzs I972 3.686930 sum 3 or 3 INTENSITY.

FIG. 6

x H m 5 FIG. 7 k E I INVENTORS 0- Duane l Kniebes I I I .1. AdrianChisholm O I I/Ml p 4 BY Robe c. Stubbs mm L ,j'nll mf fi/wr/A/g fA/n/qATTYS.

METHOD FOR MEASURING ODOR LEVEL IN NATURAL GAS This invention relates toa method and apparatus for measuring odor level in natural gas.

Most, if not all, utility gas companies are required by law to odorizethe natural gas delivered to the consumers thereof, as a safetyprecaution. If a gas leak exists, the odorized gas is detected and thegas leak can be reported. However, if the odor level or intensity is toolow, a gas leak may not be detected and serious consequences may occur.If the odor level is too high, on the other hand, the utility gascompanies usually receive a large number of leak complaints, many ofwhich are of no consequence, but must still be checked out. In thislatter case, the majority of these complaints are a result of the slightquantities of gas that escape prior to ignition of the flame in gasstoves and the like. There is, therefore, an optimum odor level whichthe utility gas companies generally try to maintain.

Present methods of measuring odor level, however, are considered lessthan fully satisfactory by many utility gas companies, due to the needfor a judgement by an operator to obtain a measurement. The most commonmethod presently used is to determine odor thresholds by sniffinggas-air mixtures. The gas company personnel accomplish this with aportable odorometer in which the flowing gas-air mixtures can beaccurately prepared and presented to an observers nose. Although thesame operator can usually repeat his readings on successive gas samples,different operators obtain somewhat different results because of normalvariations in olfactory sensitivity among people. Accordingly, mostutility companies are seeking an instrument or method of determiningodor level which is less dependent upon the olfactory sensitivity of itsoperator.

The method and apparatus of the present invention, while applicablegenerally to measure sulfur compounds in gases, is particularlyapplicable to directly and objectively measure odor level in naturalgas. The apparatus responds selectively to sulfur compounds in naturalgas and produces an output signal proportional to the odor level of thegas, in the same manner as an average nose. A set of odor intensityfactors developed empirically are applied to the output signal toprovide a numerical value which expresses odor intensity of the gas interms of a reference odorant compound.

The apparatus may be described as a dual column gas chromatographequipped with a sulfur specific flame photometric detector. A gas sampleis injected into the apparatus and as each compound emerges it is sensedby the detector which, in turn, operates a recorder to record a peakthat indicates the quantity of that compound present in the sample. Thetime at which each peak appears identifies the specific compound beingmeasured in the sample. The concentration of each of the specificcompounds is determined, and then the empirically determined odorintensity factors are applied to calculate the contribution of each ofthese compounds to the odor level of the gas. The results are summed andthe calculated value is a number that expresses the odor level of thegas in terms of the concentration of a pure reference compound thatwould give an equivalent odor. These latter computations preferably arederived electronically and the calculated value digitally displayed onthe display device. By knowing the necessary concentration of the purereference compound necessary or desirable to establish an acceptableodor level in the natural gas, the operator can easily and quicklydetermine whether the measured odor level is within an acceptable range.

In addition to recording and digitally displaying the measured odorlevel in the above-described fashion, the apparatus can be used incombination with an odorizing device to operate the latter to supplyodorant material to a natural gas stream as necessary to maintain apre-established acceptable level. The apparatus therefore can also beused to monitor the odor level of a natural gas stream and to controlthe operation of an odorizing device to maintain a pre-establishedodorant level in the stream.

Accordingly, it is an object .of the present invention to provide animproved method and apparatus for directly and objectively measuringodor level in natural gas.

A still further object is to provide improved apparatus of the describedtype which provides an indication that expresses the odor level of thenatural gas in terms of the concentration of a pure reference compoundthat would give an equivalent odor level.

Still another object is to provide improved apparatus of the describedtype which is operable in combination with an odorizing device tomaintain a pre-established odorant level in a natural gas stream.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a perspective view of a test room exemplary of the test roomused to conduct relative odor intensity tests;

FIG. 2 is a view generally illustrating the manner in which the odorizedair is supplied to the odor chambers of the test room of FIG. 1;

FIG. 3 is a pictorial-type perspective view of an instrument exemplaryof the invention for measuring sulfur compounds in gases;

FIG. 4 is a block diagram-type schematic of the instrument of FIG. 3;

FIG. 5 is an illustration of an odor profile derived from the instrumentof FIGS. 3 and 4; and

FIGS. 6 and 7 are two additional illustrations of odor profiles found intwo sources of natural gas.

Similar reference characters referred to similar parts throughout theseveral views of the drawings.

The instrument of the present invention, as indicated above, respondsselectively to sulfur compounds in natural gas and produces an outputsignal proportional to the odor level of the gas as measured by anaverage nose. Accordingly, as a first step in developing the instrument,it was necessary to determine how each sulfur compound normallyencountered in natural gas contributes to the total odor level of thegas. Next, each compound had to be assigned an olfactory response factorin an equation that relates these factors to a total odor level. I

. The development of such an equation required knowledge both of theodor intensity of the individual sulfur compounds and the manner inwhich their odors combine to produce an odor level for a mixture. Theequation also had to be valid over the range of odor intensity ofinterest. Numerous prior attempts have been made to subjectively measurethe intensity of odor, however, the results generally have beenunsatisfactory, for one reason or another. The method used in thepresent invention for making these subjective measurements is unique inthat all of the measurements were made with reference to a referenceodor as a basis of comparison. Thus, an observer need only determine ifan odor is greater than, less than, or equal in intensity to that of areference. The equation developed then is used to convert sulfurcompound content to an odor intensity in terms of equivalence to aconcentration of pure reference compound. Using this method, theproblems previously encountered in trying to make similar subjectivemeasurements were overcome.

These relative odor intensities for the sulfur compounds were determinedby pa'nel tests in which observers compared pairs of odorant compoundsin side-byside tests. Mixtures were also tested to determine the waydifferent odors combine to produce the total odor imparted to naturalgas by their presence.

These tests were conducted in a test room 10, such as the oneillustrated in FIG. 1, which was specially designed and constructed forthis purpose. The test room is 8 feet wide, 12 feet long, and 8 feethigh, and is constructed of glass, aluminum, and stainless steel whichdo not retain odors or act as sources of interfering odors. Air suppliedto the test room is temperature and humidity-controlled and is filteredthrough activated charcoal. Air flow rate is approximately-1,500 cubicfeet per minute, which provides about two air changes each minute.

The odor comparison tests were carried out with two odor source chambers12 and 14 attached to the exhaust wall of the test room 10. Odorized airto these chambers 12 and 14 is supplied in the manner illustrated inFIG. 2. About 200 cubic feet of air per minute is withdrawn from theinlet plenum 16 of the test room 10, split into equal portions, andsupplied to the chambers l2 and 14. Odorant is added to the air supplyof each chamber by means of microliter pumps 18 and 19, respectively.The speed of the pumps 18 and 19 and the size of the syringes 20 thereofare varied to produce different feed rates. The liquid odorant isinjected directly into a stream of nitrogen flowing through /4-inchtubes 21 and 22. The liquid odorant evaporates from the needle tips 23and 24 and is carried to the air ducts 25 and 26 where perforated tubes27 and 28 dispense the vapor uniformly into the air streams to thechambers 12 and 14.

The test procedure consisted of having a number of individuals on a,panel determine the relationship between odor intensity and compositionof odorant mixtures by comparing the odor intensities of pure compoundsand their mixtures. The test procedure consisted of supplying the twoodorant chambers 12 and 14 with air streams containing knownconcentrations of different odorants. The concentration of the odorcompound in one of the odor chambers 12 and 14 was maintained constantfor use as a reference. The concentration of the odor compound in theother one of the odor chambers 12 and 14 was varied stepwise, and ateach level each of the observers was asked to make a judgement ofrelative intensities. Aseries of comparisons at different concentrationsproduced one concentration which each observer judged to be equal inodor intensity to the reference, and a number of other comparisons wherethe odor was judged to be weaker or stronger than the reference. Ameasure of consistency and repeatability was thereby obtained.

Using the data determined from these odor equivalence tests, therelative odor intensities were determined for a number of sulfurcompounds, particularly those which contribute to the odor intensity ofnatural gas. The relative odor intensities of a number of the sulfurcompounds which contribute to the odor intensity of natural gas, asdetermined in the manner described above, are set forth below in TableI, using n- Butyl Mercaptan as a reference compound.

Referring now to FIG. 3, the instrument 30 for directly measuring thesulfur compounds in natural gas and for translating this measurementinto the odor intensity of the gas can be seen to include an analyzermodule 31, a gas supply module 32 and a display module 33 including arecorder 34 which may be a strip-chart recorder and a digital display35. These modules are designed for portability so that the instrument 30can be easily transported and assembled for operation, by a singleoperator. The instrument 30 operates essentially as a special-purposechromatograph in that its detector, column, and operating conditionshave been selected so that a response is obtained only to those sulfurcompounds that contribute odor to natural gas. The response is an odorprofile which,

upon being recorded by the recorder 34, is of the type shown in FIG. 5.This odor profile is provided in less than 6 minutes.

The analyzer module 31, as can be best seen in FIG. 4 which is a blockdiagram-type schematic of the instrument 30 includes a gas samplingvalve 38, a liquid sample injection port 39, a column switching valve52, a chromatographic column 40 including a pair of columns 50 and 51which are contained in temperature-controlled ovens 41 and 41a,respectively, and a flame photometric detector 42 with its associatedphotomultiplier tube and amplifier circuits for providing an outputsignal to the display module 33.

The gas supply module 32 contains three sources of analyzer module 31.These gases are contained in small, high-pressure spherical bottles 45,46, and 47, respectively, that are equipped with miniature, 2-stageregulators 48. Valves and flowmeters (not shown) also are provided forsupplying exact flows of each gas to the chromatographic column 40 andthe detector 42. Nitrogen is used as the carrier gas in thechromatographic column 40 and is mixed with oxygen at the burner base inthe detector 42. Hydrogen is supplied for the burner fuel and to providea reducing atmosphere. Sufficient hydrogen is carried in the gas supplymodule 32 for 40 hours of continuous operation, while the oxygen andnitrogen supply will last for 160 hours because of the lower flow ratesused. When installed as a permanent installation as a control instrumentfor controlling the operation of an odorizing apparatus, the gas supplymodule 32 advantageously is replaced with a continuous supply of gasesfor operating the analyzer module 31.

The chromatographic column 40 of the analyzer module 31 includes the twocolumns 50 and 51, each of which is in the form of three-sixteenths-inchstainless steel tube, 3% feet in length, packed with silanized Porapak Qcoated with 5 percent silicone oil QFl-6500. Other packings for thecolumns 50 and 51 can be used which separate the sulfur compounds,however, it has been found that the use of this silanized packing coatedwith silicone oil effectively prevents loss of the sulfur compounds byadsorption on the packing material. With many other types of packing,substantial loss of these compounds by adsorption on the packingmaterial is experienced.

The column 50 is operated at approximately 30-4O C and is used todetermine compounds boiling in the range of hydrogen sulfide to methylmercaptan. The

column 51, on the other hand, is operated at approximately l60-l80C, andis used to determine compounds boiling in the range of ethyl mercaptanto normal amyl mercaptan.

The flame photometric detector 42 is sensitized to sulfur and measuresthe odorant compounds eluting from the chromatographic column 40. Thisdetector 42 may be a Micro Tek flame photometric flame emission detectorwhich is highly sensitive to sulfur and can respond to as little as 5parts per billion of mercaptan in a 25 ml gas sample. The detector 42also is insensitive to hydrocarbons. Only the light natural gashydrocarbons produce any interference, and this occurs prior to theelution of odorant sulfur compounds.

The flame photometric detector 42 is physically similar to a hydrogenflame ionization detector, however, in this application, a hydrogen-richatmosphere surrounds the flame, and light emitted from the region abovethe flame cone is monitored by a photomultiplier tube. When sulfur ispresent in the sample being burned in the flame, a blue light with awavelength of 394 millimicrons is emitted. An optical filter allows onlylight of this wavelength to impinge on the photomultiplier tube. Theoutput of the photomultiplier tube therefore is proportional to theintensity of light, which, in turn, is proportional to the quantity ofsulfur passing through the flame.

As each sulfur compound elutes from the chromatographic column 40, theamplifier circuits (not shown) associated with the detector 42 providean output to the display module 33, to indicate the quantity of thatcompound present in the sample. The time at which each compound elutesfrom the chromatographic column 40, as indicated by the peaks recordedby the recorder 34, in the manner described more fully below, identifiesthe specific compound being measured in the sample.

A typical test of gas odor level with the instrument 30 can be describedas follows. The natural gas to be analyzed is connected to the stainlesssteel gas sampling valve 38 which is the inlet port of the analyzermodule 31. Prior to testing a sample of natural gas, the instrument 30preferably is first calibrated, by injecting a liquid standard in theform of a known concentration of a sulfur compound in alcohol into it.About 15 minutes are required to stabilize the oven temperature from anambient temperature start. The liquid standard, as well as the gassamples, requires approximately 6 minutes to elute from thechromatographic column 40, to provide an odor profile, as explained morefully below.

In Table 1 above, the retention time, in minutes, of a number of themost commonly encountered odorants in natural gas are tabulated. As eachof the sulfur compounds elutes from the column 40, they are detected bythe flame photometric detector 42, in the manner described above, and anoutput is provided to the display module 33. The recorder 34 of thedisplay module 33 is operated thereby, to provide an odor profile in theform of one or more recorded peaks, each separated by a period of time.

Assuming that the odor profile of FIG. 5 was recorded by the recorder34, upon injecting the liquid standard into the instrument 30, and byreferring to this odor profile and Table 1, it can be seen that theliquid standard is an odor mixture of, from left to right, the sulfurcompounds dimethyl sulfide, isopropyl mercaptan, tert-butyl mercaptan,n-butyl mercaptan, and thiophane. The results of this calibration runare used to confirm proper operation of the instrument, and to allowadjustments to be made for slight shifts in instrument sensitivity andcolumn performance.

After the instrument 30 has been calibrated, the gas sampling valve 38is rotated, to inject a 25 ml sample of the natural gas into thechromatographic column 40. As indicated above, nitrogen is used as acarrier gas to flush the sample through the column 40. Again, as each ofthe sulfur compounds elutes from the column 40, they are detected by theflame photometric detector 42 and the odor profile is recorded by therecorder 34.

Several representative odor profiles which may be recorded are shown inFIGS. 6 and 7. From these odor profiles and the retention times listedin Table 1, it can be seen that the odor mixtures of FIGS. 6 and 7 areboth tert-butyl mercaptan types, as evident from the large peak thatoccurs just after 2 minutes. The smaller peak in FIG. 6 shows that theodorant also contains dimethyl sulfide, and the smaller peak in FIG. 7shows that this odorant also contains isopropyl mercaptan.

Using the recorded odor profile, the total odor intensity of the gas canbe determined. This may be accomplished as follows. The area under eachrecorded peak is determined, in a manner well-known in the field ofchromatography, and then the concentration of the odorant is determinedby comparing the determined value with a known standard of the sameodorant. For example, assume that the area under the dimethyl sulfidepeak in FIG. 6 is determined to be 500 mm and that it is known that anequal volume of a standard sample containing 2 parts per million (ppm)of dimethyl sulfide provides a peak having an area of 400 mm". From theequation,

it is determined that the'concentration of dimethyl sulfide in the gasis 2.5 ppm.

Having now determined the concentration of the dimethyl sulfide in thegas, its odor intensity is determined by applying the relative odorintensity from Table 1, in this case 0.74, to the concentration inaccordance with the equation,

2.5 ppm X 0.74

to determine that its odor intensity is. 1.85 in terms of theconcentration of the pure reference compound which, in this case, isn-butyl mercaptan. After the odor intensity of the odorant indicated bythe second peak in FIG. 6, in this case, tert-butyl mercaptan, isdetermined in the same manner, these two computed values are added andthe result indicates that the gas has an odor equivalent to that of agas containing, for example, 4.0 ppm of n-butyl mercaptan.

Knowing this value, it can be compared to a preestablished range ofvalues indicating the acceptable range of odor level in the natural gas,for n-butyl mercaptan. In the case of n-butyl mercaptan, an acceptablerange may be, for example, l-l ppm of n-butyl mercaptan. Accordingly,the odor level of the gas in the above assumed example would be withinthe acceptable range.

Results of the mixture tests indicate that a number of the sulfurcompounds such as, for example, the mercaptans and thiophane, areadditive in producing a total odor intensity. The sulfides, on the otherhand, gave indications of synergism with some mercaptans, resulting inan enhanced odor intensity. Accordingly, in those cases where the odorprofiles indicate that the gas contains a mixture of odorants, such asin the case of the odor profiles of FIGS. 6 and 7, the odor intensity ofeach of the detected sulfur compounds is determined in the mannerdescribed above and then all are added to provide an indication of thetotal odor intensity. In those cases where a synergistic effect isindicated, the enhancement of the odor intensity can be compensated forby applying a compensating factor.

The instrument 30 is adapted to perform the above mathematicalcomputations electronically, and to provide a numerical value read-outof the total odor intensity on the digital display 35. As can be .bestseen in FIG. 4, the display module 33 includes a converter 36 includedin the coupling between the output of the flame photometric detector 42and the inputs to the recorder 34 and the digital display 35. Thisconvertor 36 determines the concentrations of each sulfur compound, andapplies the relative odor intensity factor to each of the determinedconcentrations and then adds the results to thereby compute the totalodor intensity so that the numerical value displayed by the digitaldisplay 35 indicates that the gas has an odor equivalent to that ofa-gas containing the indicated concentration of a pure referencecompound. With this digital indication, it therefore can be easily andquickly determined whether the odor level of the gas is within theacceptable range.

The instrument 30, as indicated above, also can be used to control theoperation of an odorizing apparatus suchas a variable rate pump thatpumps liquid odorants into a natural gas pipeline. Odorizing apparatusof this type is commonly controlled only by a gas flow rate sensor sothat a pre-established volume of liquid odorant is evaporated into agiven volume of natural gas. In such an application, the instrument 30is adapted so that a sample of the odorized natural gas is periodicallyinjected into the chromatographic column 40. The odorants are detectedand measured in the manner described above, and the output of theconverter 36 is coupled to the odorizing apparatus 60 via the conductor61, as illustrated in FIG. 4. If the odor level is below apre-established minimum acceptable level, the odorizing apparatus 60 isoperated to supply additional odorant material to the natural gasstream.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efl'iciently attained andcertain changes may be made in carrying out the above method and in theconstruction set forth. Accordingly, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

Now that the invention has been described, what is claimed as new anddesired to be secured by Letters Patent is:

1. A method for measuring odor intensity of sulfur compounds in gas interms of a reference compound comprising the steps of: separating thedifierentsulfur compounds in a predetermined volume sample of said gas;detecting each of said separated sulfur compounds;

determining the concentration of each of said separated and detectedsulfur compounds; and determining the odor intensity of an equivalentconcentration of said reference compound by applying to said determinedconcentrationof each of said separated and detected sulfur compounds arelative odor intensity factor empirically determined by havinga panelof individuals sniff different concentrations of each of a plurality ofdifferent sulfur compounds and compare the odor thereof with a knownconcentration of said reference compound to determine the concentrationof each of said plurality of different sulfur compounds which isequivalent in odor intensity to said known concentration of saidreference compound.

2. The method of claim 1, further including the step of: summing thedetermined odor intensity of an equivalent concentration of saidreference compound for each of said separated and detected sulfurcompounds to provide a determination of the total concentration of allof said separated and detected sulfur compounds in said sample of gas interms of the odor intensity of an equivalent concentration of saidreference compound.

3. The method of claim 2, further including the step of: comparing thedetermined odor intensity of an equivalent concentration of saidreference compound with a pre-determined range of concentrations of saidreference compound which is known to provide an acceptable odorintensity level in gas, to thereby provide a means of determiningwhether the odor intensity of said gas is at an acceptable level.

4. The method of claim 1, comprising the steps of separating thedifferent sulfur compounds in a predetermined volume sample of said gasusing a gas chromatograph; detecting each of said separated sulfurcompounds using a sulfur specific detector which provides an electricaloutput signal representative of the concentration of each of therespective ones of said separated and detected sulfur compounds;recording each of said electrical output signals to as to provide anodor profile of the sulfur compounds in said gas; determining theconcentration of each of said separated and detected sulfur compoundsfrom said recorded odor profile; and determining the odor intensity ofan equivalent concentration of said reference compound by applying saidrelative odor intensity factor to said determined concentration of eachof' said separated and detected sulfur compounds.

5. The method of claim 4, further including the step of: summing thedetermined odor intensity equivalent concentrations of said referencecompound for each of said separated and detected sulfur compounds toprovide a determination of the total concentration of all of saidseparated and detected sulfur compounds in said sample of gas in termsof the odor intensity of an equivalent concentration of said referencecompound.

6. The method of claim 5, comprising the steps of separating thedifferent sulfur compounds in a predetermined volume sample of said gasusing a gas chromatograph; detecting each of said separated sulfurcompounds using a sulfur specific detector which provides an electricaloutput signal representative of the concentration of each of therespective ones of said separated and detected sulfur compounds;recording each of said electrical output signals so as to provide anodor profile of the sulfur compounds in said gas; deter-, mining theconcentration of each of said separated and detected sulfur compoundsfrom said recorded odor profile and determining the odor intensity of anequivalent concentration of said reference compound by applying saidrelative odor intensity factor to said determined concentration of eachof said separated and detected sulfur compounds.

7. The method of claim 1, comprising the steps of separating thedifferent sulfur compounds in a predetermined volume sample of said gasusing a gas chromatograph; detecting each of said separated sulfurcompounds using a sulfur specific detector which provides an electricaloutput signal representative of the concentration of each of therespective ones of said l0 separated and detected sulfur compounds;determining the concentration of each of said separated and deseparatedand detected sulfur compounds in terms of the odor intensity of anequivalent concentration of s 'd refe e ce co un d' an rovidin numericaldiiplay o e total or intensity? of an egu ivalent concentration of saidreference compound using an electrical digital display device which isresponsive to the electrical output signal from said convertor means.

8. The method of claim 7, further including the steps of recording eachof said electrical output signals from said detector so as to provide anodor profile of the sulfur compounds in said gas.

9. The method of claim 1, comprising the steps of separating thedifi'erent sulfur compounds in a predetermined volume sample of said gasusing a gas chromatograph; detecting each of said separated sulfurcompounds using a sulfur specific detector which provides an electricaloutput signal representative of the concentration of each of therespective ones of said separated and detected sulfur compounds;determining the concentration of each of said separated and detectedsulfur compounds, determining the odor intensity of an equivalentconcentration of said reference compound of each of said separated anddetected sulfur compounds and summing the determined odor intensityequivalent concentrations of said reference compound using electricalconvertor means which is responsive to said electrical output signalsfrom said detector and is operable to provide an electrical outputsignal representative of the total concentration of said separated anddetected sulfur compounds in terms of the odor intensity of anequivalent concentration of said reference compound; and operating anodorizing

1. A method for measuring odor intensity of sulfur compounds in gas interms of a reference compound comprising the steps of: separating thedifferent sulfur compounds in a predetermined volume sample of said gas;detecting each of said separated sulfur compounds; determining theconcentration of each of said separated and detected sulfur compounds;and determining the odor intensity of an equivalent concentration ofsaid reference compound by applying to said determined concentration ofeach of said separated and detected sulfur compounds a relative odorintensity factor empirically determined by having a panel of individualssniff different concentrations of each of a plurality of differentsulfur compounds and compare the odor thereof with a known concentrationof said reference compound to determine the concentration of each ofsaid plurality of different sulfur compounds which is equivalent in odorintensity to said known concentration of said reference compound.
 2. Themethod of claim 1, further including the step of: summing the determinedodor intensity of an equivalent concentration of said reference compoundfor each of said separated and detected sulfur compounds to provide adetermination of the total concentration of all of said separated anddetected sulfur compounds in said sample of gas in terms of the odorintensity of an equivalent concentration of said reference compound. 3.The method of claim 2, further including the step of: comparing thedetermined odor intensity of an equivalent concentration of saidreference comPound with a pre-determined range of concentrations of saidreference compound which is known to provide an acceptable odorintensity level in gas, to thereby provide a means of determiningwhether the odor intensity of said gas is at an acceptable level.
 4. Themethod of claim 1, comprising the steps of separating the differentsulfur compounds in a predetermined volume sample of said gas using agas chromatograph; detecting each of said separated sulfur compoundsusing a sulfur specific detector which provides an electrical outputsignal representative of the concentration of each of the respectiveones of said separated and detected sulfur compounds; recording each ofsaid electrical output signals to as to provide an odor profile of thesulfur compounds in said gas; determining the concentration of each ofsaid separated and detected sulfur compounds from said recorded odorprofile; and determining the odor intensity of an equivalentconcentration of said reference compound by applying said relative odorintensity factor to said determined concentration of each of saidseparated and detected sulfur compounds.
 5. The method of claim 4,further including the step of: summing the determined odor intensityequivalent concentrations of said reference compound for each of saidseparated and detected sulfur compounds to provide a determination ofthe total concentration of all of said separated and detected sulfurcompounds in said sample of gas in terms of the odor intensity of anequivalent concentration of said reference compound.
 6. The method ofclaim 5, comprising the steps of separating the different sulfurcompounds in a predetermined volume sample of said gas using a gaschromatograph; detecting each of said separated sulfur compounds using asulfur specific detector which provides an electrical output signalrepresentative of the concentration of each of the respective ones ofsaid separated and detected sulfur compounds; recording each of saidelectrical output signals so as to provide an odor profile of the sulfurcompounds in said gas; determining the concentration of each of saidseparated and detected sulfur compounds from said recorded odor profileand determining the odor intensity of an equivalent concentration ofsaid reference compound by applying said relative odor intensity factorto said determined concentration of each of said separated and detectedsulfur compounds.
 7. The method of claim 1, comprising the steps ofseparating the different sulfur compounds in a predetermined volumesample of said gas using a gas chromatograph; detecting each of saidseparated sulfur compounds using a sulfur specific detector whichprovides an electrical output signal representative of the concentrationof each of the respective ones of said separated and detected sulfurcompounds; determining the concentration of each of said separated anddetected sulfur compounds, determining the odor intensity of anequivalent concentration of said reference compound of each of saidseparated and detected sulfur compounds and summing the determined odorintensity equivalent concentrations of said reference compound usingelectrical convertor means which is responsive to said electrical outputsignals from said detector and is operable to provide an electricaloutput signal representative of the total concentration of saidseparated and detected sulfur compounds in terms of the odor intensityof an equivalent concentration of said reference compound; and providinga numerical display of the total odor intensity of an equivalentconcentration of said reference compound using an electrical digitaldisplay device which is responsive to the electrical output signal fromsaid convertor means.
 8. The method of claim 7, further including thesteps of recording each of said electrical output signals from saiddetector so as to provide an odor profile of the sulfur compounds insaid gas.
 9. The method of claim 1, comprising the steps of separatingthe different sulfur compounDs in a predetermined volume sample of saidgas using a gas chromatograph; detecting each of said separated sulfurcompounds using a sulfur specific detector which provides an electricaloutput signal representative of the concentration of each of therespective ones of said separated and detected sulfur compounds;determining the concentration of each of said separated and detectedsulfur compounds, determining the odor intensity of an equivalentconcentration of said reference compound of each of said separated anddetected sulfur compounds and summing the determined odor intensityequivalent concentrations of said reference compound using electricalconvertor means which is responsive to said electrical output signalsfrom said detector and is operable to provide an electrical outputsignal representative of the total concentration of said separated anddetected sulfur compounds in terms of the odor intensity of anequivalent concentration of said reference compound; and operating anodorizing device to supply additional odorant material to the gas fromwhich said sample of gas was taken when said electrical output signalfrom said convertor means is of a value corresponding to a concentrationof said reference compound less than a pre-established minimumacceptable odor level, to thereby maintain an acceptable odor level insaid gas.